Techno-economic, environment and risk analysis of an aircraft concept with turbo-electric distributed propulsion

Abstract

The commercial aviation industry has always been driven by the need to grow and increase profitability. This has led to the evolution of aircraft from the early jets capable of carrying tens of passengers to current large airliners capable of carrying hundreds of passengers across the globe. Whilst these aircraft look superficially similar to their predecessors, they are significantly more efficient, thanks to the continuous evolution of technology. However, new aircraft are bound to increasingly stricter targets that aim to develop an environmentally sustainable industry for the future. Previous technological development has largely focused on reducing fuel consumption through iterative improvements. However, new emissions and noise targets have been set that necessitate dramatic leaps in technology. To achieve these goals, revolutionary technologies are the subject of research in the aerospace sector. Research focus predominantly focuses on proving the technological viability of these novel concepts. The aim is generally to ensure that concepts are feasible and capable of meeting performance targets. However, commercial aviation is a profit-oriented industry. It is therefore vital to ensure that concepts are economically as well as environmentally sustainable. This form of study is more rarely seen but is vital in ensuring that aviation remains both environmentally and economically sustainable. This research presents the development of a techno-economic and environmental risk assessment (TERA) framework that combines the performance and economic aspects of an aircraft in order to inform a conclusion as to the aircraft’s viability. The methodology addresses two key questions. How can an operator differentiate competing concepts when they are designed for similar performance targets? How can the economic viability of a novel aircraft concept be predicted when there is no historical data on which cost estimates can be based? The research focuses on a case study of NASA’s N3-X, a blended wing body aircraft concept with a turbo-electric distributed propulsion system and boundary layer ingestion. In order to quantify economic viablity, it was first necessary to identify the performance benefits offered by the novel aircraft configuration. Modelling methodologies were therefore developed to simulate novel propulsion systems that utilise boundary layer ingestion and distributed propulsion. In particular, a methodology was developed to address a gap in literature with respect to simulating the off-design performance of such propulsion systems. Performance simulation demonstrates that the aircraft is able to meet the 60% fuel saving target versus the baseline aircraft for the design mission. The high fuel saving of the N3-X in comparison to the baseline aircraft has the potential to provide direct operating cost saving of up to 21% versus the baseline aircraft. This enables the manufacturer to offer the aircraft at a higher acquisition price, whilst retaining an attractive product for customers. Economic viability of the aircraft is more limited for short haul mission ranges, as fuel is a less dominant factor for the aircraft’s direct operating cost. Acquisition cost estimation suggests that the aircraft could achieve the cost target for an economically viable aircraft. This cost estimate is associated with a reasonable number of aircraft sales that could feasibly be supported by the future aircraft market for large widebodies. However, viability is closely tied to the economic environment, especially factors such as the current fuel price or environmental taxation levels. In particular, low fuel price reduces the financial value of high efficiency technology, and hence the maximumeconomical viable price of the aircraft is lower. The research also performs a design space exploration for the case study aircraft. This included the assessment of liquid hydrogen as an alternative to conventional kerosene and the exploration of alternative configurations for the propulsion system. As the final stage of the TERA analysis of the aircraft, a risk assessment was also performed to identify those technologies and factors that may have the greatest influence over the aircraft’s viability. The methods developed in this research open up a wide range of activities for further work in both the performance and techno-economic aspects of the research. Further design space exploration is possible, particularly with respect to the propulsion system design. In addition, the TERA framework may be used to assess alternative novel aircraft concepts to identify aircraft and technology combinations that may benefit most from further investment.